Search

Sintetizzare nuovi materiali ibridi organo-inorganici è da sempre l’interesse di molti ricercatori in quanto possiedono particolari proprietà che li rendono utili per diverse applicazioni (sensori ottici e chimici, componenti bioattivi nelle protesi, materiali isolanti nei circuiti microelettronici). L’utilizzo del metodo sol-gel rappresenta una tecnica promettente per la produzione di tali materiali. Attraverso questa metodologia, sono stati sintetizzati materiali ibridi utilizzando TiO2 e polieterimmide (PEI) al 6 e 12% in peso. L’interazione tra la fase organica ed inorganica è stata studiata attraverso la Spettroscopia Infrarossa con Trasformata di Fourier (FTIR), mentre la microstruttura è stata osservata con l’uso del microscopio a scansione elettronica (SEM), il microscopio a forza atomica (AFM) e diffrazione ai raggi X (XRD). Al fine di valutare la bioattività, è stata determinata la capacità di formare idrossiapatite attraverso il saggio di Kokubo[1] ed osservata con il SEM e la spettroscopia a dispersione energetica (EDS).

La progettazione di nuovi catalizzatori eterogenei selettivi richiede la definizione di procedure di preparazione mirate, affiancate da un approccio di caratterizzazione basato su più tecniche chimico-fisiche. In questo contributo, saranno presentati esempi relativi all'ottimizzazione di nuovi catalizzatori solidi contenenti centri metallici cataliticamente attivi ottenuti a partire da argille sintetiche, un supporto versatile che può essere modificato in modo razionale per introdurre nuove ed interessanti funzionalità.

The research activity of this thesis is focused on the development and optimization of new directly patternable organically modified TiO2, Al2O3 and ZrO2 based sol-gel materials whose peculiar characteristics and performances were optimized and exploited for the final specific application. In particular, the main strategy that lies at the basis of all the thesis work is the combination of top down and- bottom up approach for the final device realization. In fact, special attention has been set to materials design and synthesis (bottom up) and subsequently to the micro- and nano- fabrication of patterns on the corresponding film surface with different lithographic techniques (top down) in order to achieve the required properties, according to the final application. As it concerns the bottom up approach, the sol-gel has been assumed as the main synthetic method since, by mixing different organic-inorganic precursors, new materials with unique properties and microstructures can be created. In fact, by using organically modified precursors (such as trimethoxyphenylsilane, 3-glycidoxypropyltrimethoxysilane, 3-(Trimethoxysilyl)propyl methacrylate) or organic monomers it was possible to produce hybrid materials with the organic and inorganic components intimately mixed at a molecular scale, with the twofold effect of obtaining new properties and conferring them the patternability. Moreover, the addition of tetrafunctional precursors (Titanium isopropoxide, Zirconium butoxide, Aluminum-tri-sec-butoxide) allowed to increase the reticulation degree, taking part to the inorganic network formation, to improve the material mechanical properties (such as scratch, abrasion, plasma etching resistance) and to confer particular characteristics to the final materials, i.e. to modulate the refractive index. On the other hand, as it regards the top down approach, different lithographic techniques (photolithography, X-ray lithography, electron beam lithography and nanoimprint lithography) have been exploited in the realization of high refractive index patterns, high selective etching masks features, adaptive-optics devices and stamps for microinjection moulding directly with the synthesized materials. The structural and chemical changes induced inside the material by the interactions with the source used in the lithographic process have been deeply investigated in order to optimize both the synthesis of the best sol-gel systems and the final lithographic procedures. In conclusion the development of all the above mentioned advanced materials and innovative processing was pushed by the main target of improving, simplifying and decreasing costs and time of the overall micro- and nano- fabrication process in order to obtain better final features quality, with respect to traditional lithographic procedures.

"The research develops new hybrid biomimetic materials that work as mechanically stimulating “scaffolds” to promote early regeneration in implanted bone healing phases. A modified commercial odontostomatological implant has been biomechanically investigated by Finite Element Analysis. A biomimetic nanostructured osteoconductive material has been used to replace part of the implant screw. Combined material characterization (mechanical and aqueous media sorption behaviour) and computer-aided simulations have been carried out. Such biomimetic multidisciplinary approach allowed us to explore many novel ideas in modelling, design and use of new nanostructured biomaterials and devices with enhanced functionality and improved interaction with Osteoblast cells."

We have studied the interactions in the solid phase between a blue-light-emitting organic conjugated polymer {poly[(9,9-dihexylfluorenyl-2,7-diyl)-alt-co-(9,ethyl-3,6-carbazole)]} and colloidal CdSe/ZnS core shell quantum dots. We demonstrate by time resolved photoluminescence measurements that efficient Forster energy transfer takes place from the polymer acting as the donor and the CdSe/ZnS dots, acting as the acceptors. A Forster radius of about 80+/-15 Angstrom is extracted from the analysis of the relaxation dynamics based on the solution of the donor-acceptor coupled rate equations. This value is in good agreement with the value extracted from the steady state spectra and indicates that efficient energy tranfer from a polymeric host to a nanocrystal guest can occur. Our results are relevant to the application of hybrid organic/inorganic systems to light-emitting devices.

By reaction of lead(II) nitrate with P,P'-diphenylmethylenediphosphinic acid in water solution a new inorganic-organic hybrid of formula [Pb(CH2(P(Ph)O2)2)] has been synthesized and structurally characterized. The complex displays a polymeric columnar structure, the column being formed by two intersecting sinusoidal ribbons of lead(II) ions bridged by bifunctional phosphinate ligands. The intersections of the ribbons are constituted by dimeric units of pentacoordinated lead(II) ions.

New organic-inorganic hybrid materials have been synthesized by reaction in water solution of manganese, cobalt or nickel acetates with P,P'- diphenylmethylenediphosphinic acid and all the two-dimensional structure coordination polymers obtained have been found to be isomorphous.

(3-Glycidoxypropyl)trimethoxysilane (GPTMS) derived hybrid organic-inorganic materials have been obtained by a new multistep nonhydrolytic/hydrolytic synthesis. The new synthesis has been achieved using titanium(IV) chloride instead of titanium alkoxides to catalyze the epoxy ring opening in the organically modified alkoxide. The precursor sols were studied by multinuclear solution-state magnetic resonance (NMR) techniques, gas chromatography coupled with mass spectrometry (GC-MS), and electrospray ionization (ESI) experiments. The derived powdered gels were characterized by multinuclear solid-state magic angle spinning (MAS) NMR, Fourier transform infrared (FT-IR), and matrix-assisted laser desorption/ionization (MALDI) experiments. All these results show that epoxy ring opening is achieved at low temperature and within short reaction times. Interestingly, several reactions occur simultaneously and are involved in the early polymerization process, leading to fast catalyst deactivation in solution, chlorination of GPTMS organic groups, and titanium dispersion inside precursor sols. Despite a rather complex reaction pathway, this method can be used to prepare transparent hybrid organic-inorganic materials, whose properties can satisfy the requirements for photonic applications.